Difference between revisions of "OOP Class6"

Revision as of 22:14, 17 June 2008

Review

Accessibility

restrict the visibility of a class and it's members

Classes

Abstraction that has properties and methods. properties and the nouns and methods are the verbsClasses are used to define objects.

Objects

Instance of a class

Abstraction 

Factor out details to work on fewer concepts at a time

Encapsulation

Allows us to use objects with out completely understanding how everything inside the object works. Encapsulation also allows the internal state of objects to be changed easily without affecting other objects or interfaces. Real barking dogs...DogBark an example of how you don't need to know how all of the classes work just how to use them

Polymorphism

many forms that have the same attributes and abilities

UML 

Unified Modeling Language.

TODO

Virtual Functions

Functions that can be overridden.

Static

Members that are associayed with a class not an instance of the class

Shared Members - static members

aka Shared Properties

Static - A type of member modifier that indicates that the member applies to the type rather than an instance of the type

<csharp>public class Dog { //some code

static private int dogCount; // total number of dogs

public Dog() { barkSound = "Woof!!!";

		//Add a dog to the total dog count

dogCount++; } public Dog(string newName) { name = newName; barkSound = "Woof!!!"; //Add a dog to the total dog count dogCount++; }</csharp> }

Static dougCount Example
dogStatic.cs - source

OverLoading

You can overload a method to make it more flexible.

Simple Bark Method

<csharp> public class Dog {

	public string Name;		// the dog's name

public string BarkSound; // the sound of the dog's bark

public Dog() { BarkSound = "Woof!!!"; }

public string Bark() { string strBark = this.BarkSound;

               barkCount ++;
               return strBark;

}

public void Eat() { //put eat code here } } </csharp>

overloaded method that makes a dog bark more than once.

<csharp> public class Dog {

	public string Name;		// the dog's name

public string BarkSound; // the sound of the dog's bark

public Dog() { BarkSound = "Woof!!!"; }

public string Bark() { string strBark = this.BarkSound;

               barkCount ++;
               return strBark;

}

public string Bark(int numBarks) { string strBark = "";

               for(int i =0; i < numBarks; i++)  //bark many times
               {
                  strBark += this.BarkSound;
                  barkCount ++;
               }
               return strBark;

} } </csharp>

You can overload a method as much as you want as long as each overload has a unique argument signature

Overload Constructor

Overloading the constructor of you class can make it easier to use.

here is a simple dog contructor

<csharp> public class Dog {

public string BarkSound; // the sound of the dog's bark

public Dog() { BarkSound = "Woof!!!"; }

} </csharp>

we can modify this so that we can pass in the sound of the dogs bark when the object is created

<csharp> public class Dog {

public string BarkSound; // the sound of the dog's bark

public Dog(string newBarkSound) { this.BarkSound = newBarkSound; }

} </csharp>

or the name of the dog and the barksound

<csharp> public class Dog {

public string BarkSound; // the sound of the dog's bark

       public string Name;

public Dog(string newBarkSound, string NewName) { this.BarkSound = newBarkSound;

               this.Name = newName;

}

} </csharp>

you can have as many overoads as you want as long as each overload has a unique argument signature

Association - 'Uses A'

A dog uses a hydrant to relieve them self.

<csharp>//Dog simple class definition public class Dog {

   //some dog code...
   
   public void Relieve(Hydrant h)
   {
    h.Clean = false;
   }

}

public class Hydrant {

 public string Color; //the color of the hydrant
 public bool Clean;   //if the hydrant is clean or dirty
 
 public Hydrant()
 {
   Color = "red";
   Clean = true;
 }
 
 public override string ToString ()
 {
   if (this.Clean == true)
   {
    return ("The " + this.Color + " hydrant is clean.");
   }
   else
   {
    return ("The " + this.Color + " hydrant is not clean.");
   }
 }

}</csharp>

Dog Association example DogHydrant.cs - source

Containment - 'Has A'

A dog has an owner

<csharp>Dog fido = new Dog("fido"); fido.Owner = new Person("Sue");</csharp>

<csharp>//Dog simple class definition public class Dog {

   public string Name;        // the dog's name
   public string BarkSound;    // the sound of the dog's bark
   public Person Owner;    // the dogs owner
   
   public Dog(string dogName)
   {
       Name = dogName;
       BarkSound = "Woof!!!";
   }

   public string Bark() { 
       string s;
       s = this.Name + " says " + this.BarkSound;
       //Make sure the the dog has an owner
       if (!(this.Owner == null))
          s += "\n" + Owner.Name + " says be quiet.";
       return s;
   }

}

public class Person

 {
   public string Name;      //the color of the hydrant
   
   public Person(string newName)
   {
     Name = newName;
   }
 }</csharp>

Containment example
DogOwner.cs -source

Homework

READ

Create Super and Sub class fro the class you made last week

• Inheritance
• Virtual / Override
• Constructor
• Overloaded Constructors

Make me a TV and Radio class. Make a super class for TV and Radio and have them inherit from it.

Extra Credit is equal lateral Triangle, Rectangle

Finish you tv radio class and add overloads to you example class